By combining low-density RXTE long- and medium-term
monitoring with high-density, short-term monitoring from XMM
and Chandra long-looks, we have constructed X-ray
fluctuation power spectral densities (PSDs) for six Seyfert
1 galaxies. These PSDs cover unprecedented dynamic ranges,
continuously spanning up to or beyond 4 orders of magnitude
in temporal frequency. The PSDs of four targets show
significant flattening towards lower frequencies and bear
remarkable similarity to X-ray Binary PSDs, strengthening
the argument that similar emission processes occur in both
types of compact accreting systems, spanning a factor of
~106-7 in luminosity and putative black hole mass.
Assuming a linear mass-timescale relation, the resulting PSD
break frequencies imply black hole masses which generally
agree with reverberation-mapped mass estimates. If the
geometric origin of the variability is close to the X-ray
corona, then the physical timescales associated with thermal
and acoustic disk variations may be relevant.

The author(s) of this abstract have provided an email address
for comments about the abstract:
agm@astro.ucla.edu